Carburetor preheat system



Sept. 17, 1946. F. c. Ml-:LcHloR CARBURETOR PRE-HEAT SYSTEM` FiledFeb. 1. 1944 3 Sheets-Smet 1 Frederick Clelcez'or IN VEN TOR.

Sept. 17, `1946.

F.l c.fMELcHloR CARBURETOR PRE-HEAT SYSTEM 3 `Sheets-Sheet 2 Filed Feb.1, 1944 l I l Il, I..

l f f BYv Sept. 17, 1946. F. c. MELcl-noR 2,407,719

CARBURETOR PRE-HEAT SYSTEM Filed Feb. 1, 1944 3 Sheets-Sheet 3 BY` Qi/MWf H www-ww 'ventilation of the same.

Patented Sept. 17, 1946 UNITED STATES PATENT A"OFFICE 2,407,719 l I.CARBQRETOR PREHEAfr SYSTEM FiederickiflfMelchior, New York, N. Y.rApplication-rennen 1, 1944, seriali-No. 520,629'

This invention relates `to improvements in air- 'craft power plant'installations and more particularly to the use and disposal `of engineexhaust `heat and of 'the `air heated in the process 'o'f scoops for thecarburetor and for oi-l cooling.

When the cowl flaps are opened at an angle the 4deflection of the airflow 'cause'ssucti'on out of the engine compartment thereby augmentingHowever, cowl 'flaps when `opened have the undesirable :effect ofcausing turbulence disturbing the air flow aroundthe nacelle and part ofthe wing and sometimes adversely alecting the control surfaces Vtol theextent that in some current'aircraft cowlf'flaps-cannot be openedappreciably during night,

To provide adequate pre-heating ofthe 'carburetor air as an anti-icingmeasure, the `conventional installation Yalso embodies a shroud or muff,comprising in effect a continuation oft'he rear cowl, rigidly attachedto the latter and"- partially enclosing the collector well hou-sing theexhaust collector` ring or manifold. The shroud or mui is interrupted atthe top and `bottom ofthe nacelle to accommodate air scoops to vthe :eclaims. (cl. 12s- 171) through Acontact with the lexhaust fcollectoriin'g.-

This arrangement provides adequate carburetor air heat to cope withnormal iicing conditions, which has `been found not tobe thecaseiinnstallations lacking Vsuch arrangement. However,

it does not render optimum ventilationfo'fthe vide'means for proper'cooling of the exhaustcollector ring `and ventilation of the 'collectorwell, whether or not the carburetor 'heat is used, and to eliminate the`undesirablev effects Aci the cowl flaps now in current use.

The subject invention embodies -a vsliding Venturi cowl to replace theconventional cow'lflaps said Venturi cowl incorporatingrigidlylatt'ached thereto a shroud or mui partly enclosing Vthe exhaustcollector ring in thewell and extending substantially alongitheperiphe'ry. As the :nuff moves Withthe sliding Venturi cowl `thislwhole unit forms with the rear -cowl andthe diaphragm a variableVenturi opening as an `exit `aperture 'for the hot air-flowing throughthe exhaust col- 'intake scoop I5 for the oil cooler maybe provided asis the airintake or ram scoop T|16 'for the carburetor. These areusually mounted'with the scoop 'I5 at 'the bottom and the scoop f6 atVthe top ofthe `nose cowl l1. 'My invention contemplates anengine'having et-conventional exhaust collector ring 20 andan exhaustcollector well 2| *formed by a diaphragm T22 and -a lmovable v'shroudmember 23 attached to a sliding Venturi cowl `24. The shroud 23 'is soshaped as to `form with the diaphragm '2'2 `a vcollector wellAsubstantially elliptical in cross section. A fixed-shield 451separatesthe upper part of the collector well l'from'the enginecompartment, saidshield extending over a sector 'suf'ciently large to compel the coolingUair 'to ii'ow substantially along the Iexhaust Acollector well beforeentering the carburetor, when heated air is used inthe same.

The Venturi `cowl member '24 and vthe/shroud 23 are preferably made inone piece vextending yfrom the edge25 ofthe'shield 145 around tothelopposite fedge 21. However, if desired, themovable cowl Vmember "24 mayextend `Vfrom theedge "2110i the plate 445 lto theedge 28 of the oilcooling sories compartment as well `as thermal punishment of variouspertinent-parts.

An object-of the present invention fis fto proofthel nacelle, it'beingunderstood that thellength of the movable cowl '24 and'its `shroud. 23need not be limited in area. The movement of fthe `valve34v themoreheated air vable. n ,mi

In addition to the aforementioned undesirable cowl 24 and the shroud 23may be controlled manually or thermostatically by any suitable meanssuch as the thread bar 30 engaging the bracket 3| so that as the bar 30is turned theV cowl will move accordingly.

Mounted under the ram scoop I6 adjacent to where it enters the engine 33is an alternate air Valve 34 separating the collector well 2l from .theram scoop I5.' The valve 34 'may be operated in any suitable manner andit may .or vmay not be coordinated with the movement of the Venturi Ycowl 24 or, where two cowls are used, 24 and 35.

ring but as a direct consequence is obtained greatly improved cooling ofthe exhaust collector In full cold operation air will fbe" directed Ythrough the ram scoop I6 into the ,carburetor'at 3-3 as in theconventional installation.- Additional air will pass through the nosecowl H absorbingy heat from the motor l0 and cooling Ithe motor vandwill then pass into the collector well through turi slot between theslidingv cowl 24 -and the rear cowl 40 to suck the air over the motorand through the collector well around the exhaust collector ring. Withthe valve 34 closed the air going to the carburetor will be direct fromthe outside. The valve may be operated either manually orthermostatically so as to allow a, required portion of the heated airfromthe collector well -to mix with the air coming through the scoop I6.YNaturally the -greater the opening of the carburetor. I I

By operation of the Venturi cowl 24 the mass flow of air over thecylinders-can be effectively controlled. This mass flow being constantfor a given set of conditions it isfevident that the.

amount of heated air transmitted to the carburetor will depend upon theratio of the opening of the Venturi cowl 24 to that of the ,alternatevair valve 34 as heated air can only ow tothe carburetor by way of thecollector well. It is also will pass to the out the remainder, saidopening to be-governed? primarily by desired cylinder head temperatures.It follows that when no hot air is admitted to the carburetor theopening of cowl 24 mustbe correspondingly greater' and, likewise whenmaximum carburetor heat is needed, the opening of,`

cowl 24 should be barely large enough to maintain cylinder temperatureswithin permissible limits. By thus properly manipulating the Valve 34and cowl 24-the air. going into the carburetor as well as-the cylinderVAtemperatures can beef-f with the mounting ring andthe diaphragmangentrance aperture for the cooling 'airinto the collector well', saidVaperture beingalso in the nature of a Venturi slot or opening for thepurpose of providing a more uniform and effective air flow about theexhaust collector ring which-- it will be noted, is elliptical in crosssection Vfor still furtherimprovement or flow around it. Such improvedowirenders better heat transfer-'and consequently a greater degree ofpre-heat availring and ventilation of the collector well together withimproved ventilation of the engine compartment and cooling of the engineunder all conditions of iiight.

I claim- 1. In combination with an engine installation including anacelle having a nose cowl and an air. intake scoop leading to thecarburetor of said engine and an exhaust collector ring, of a carburetorpre-heat system includinga slidable cowl member extending from eitherside of said air scoop, a diaphragm extending from said engine mountingto the outer edge of said nacelle, a shroud on said slidable cowlforming with said diaphragm a collector well around said exhaustcollector ring, a valve leading from said collector well to said airintake scoop, means for selectively operating said valve and saidslidablecowl to determine the amount of air` passing through saidcollector well and the amount of air passing from said collector wellinto said air scoop.

2. In combination with an engine'installation including a nacelle havinga nose cowl and an air intake scoop leading to the carburetor of saidengi-ne, said installation including aconventional mount ring and anexhaust collector ring, adjacent thereto, of a Ventilating andcarburetor preinterior of said nacelle to the outer air, a valve leadingfrom said collector well to said air intake scoop, and means foroperating said valve to controlthe amount of air passing from saidcollector wellinto said air scoop.

3. In combination with an engine installation including a nacelle havinga nose cowl and an air intake scoop leading to the carburetor of saidengine, said engine installation including a conventional mount ring andan-exhaust collector ring, adjacent thereto, of a Ventilating andcarburetor Vpre-heating system including a diaphragm extending from saidmount ring to the outer edge of saidnacelle, a slidable cowl memberextending from either side of said air scoop, a shroud` on said-slidablecowl forming with said diaphragm a collector well around said exhaustcollector ring, means for moving said Vslidable cowl and shroud withinsaid nacelle to vary the opening from the interior of said nacelle -tothe outer air, a valve leading from said collector well to said airintake scoop,y and vmeans for operating said valve to control-the amountjof `air passing from saidcollector well-into said airscoop, said'meansbeing operated to prevent anyairfrom said collector well from passinginto'said air scoop or to mix the heated air with air from said airscoop. v .v

FREDERICK C. MELCHIOR.

